Sheet 6

Question 1

Is Tay Sachs disease dominant or recessive?

Answer 1

Recessive

Question 2

What causes Tay Sachs disease?

Answer 2

The enzyme Hexosaminidase-A that metabolizes lipids is

defective = lipid accumulation and build up = cell damage and death

Question 3

Tay Sachs disease is an example of:

Answer 3

A Classical lysosomal storage disorder

Question 4

Which gene encodes for Hexosaminidase-A?

Answer 4

HEXA gene on q arm of chromosome 15

15q – region 14

Question 5

When do clinical features start to show in Tay Sachs disease?

Answer 5

In the first months of

life

Question 6

When do Tay Sachs patients die?

Answer 6

Within the age of 3-4 yrs

Question 7

What are the clinical features of Tay Sachs disease?

Answer 7

1) Neuromotor difficulties
2) Psychomotor impairment
3) Seizures
4) Tremors
5) Other classical features of CNS damage

Question 8

In homozygous mutant individuals of Tay Sachs, the enzyme is:

Answer 8

Defective; the metabolic

activity of the enzyme is ZERO.

Question 9

In homozygous normal individuals of Tay Sachs, the metabolic activity of the enzyme is:

Answer 9

100%

Question 10

In heterozygous mutant individuals of Tay Sachs, the enzyme is:

Answer 10

Neither fully active nor inactive (incomplete dominance); metabolic activity is between 0-100%

Question 11

At the biochemical level, Tay Sachs disease is:

Answer 11

Incomplete dominant

Question 12

At the genetic/molecular level, Tay Sachs disease is:

Answer 12

Codominant

Question 13

Sickle cell anemia:

a) Phenotypically:
b) Biochemically:
c) Genetically/Molecularly:

Answer 13

a) Complete dominance
b) Incomplete dominance
c) Codominant

Question 14

Tay Sachs disease:

a) Organismal:
b) Biochemically:
c) Genetically/Molecularly:

Answer 14

a) Recessive
b) Incomplete dominance
c) Codominant

Question 15

What is an example of multiple alleles?

Answer 15

Blood groups

Question 16

What is pleiotropy?

Answer 16

1 gene defect causes multiple phenotypic effects

Question 17

Is Cystic Fibrosis dominant or recessive?

Answer 17

Recessive

Question 18

What is the Cystic Fibrosis gene?

Answer 18

CFTR

Question 19

What is an example of pleiotropy?

Answer 19

Cystic Fibrosis

Question 20

What are the phenotypic effects of Cystic Fibrosis?

Answer 20

1) Infection of air sinuses (sinusitis).
2) Mucous Build up and bacterial infection in the lungs.
3) Salty Sweating (more NaCl in sweat)
4) Biliary duct will be filled with mucous = blocked.
5) Pancreatic duct will also be blocked thus rendering the pancreatic function.
6) Intestines filled with mucous = the GI is incapable of absorbing food.
7) Complications in Males and Females reproductive organs

Question 21

Which is the easiest and typical test to start with to detect cystic fibrosis?

Answer 21

Salty Sweating

Question 22

What is Epistasis?

Answer 22

A gene at one locus alters the phenotypic expression

of a gene on another locus.

Question 23

Tay Sachs disease and Cystic Fibrosis are:

Answer 23

Single gene disorders

Question 24

Quantitative variations usually indicate which type of inheritance?

Answer 24

Polygenic inheritance, an additive effect of two or more genes on a single phenotype.

Question 25

What is polygenetic inheritance?

Answer 25

Multiple defective genes cause a disease (Multiple alleles)

Question 26

What is an example of polygenetic inheritance?

Answer 26

Skin color

Question 27

What is one thing that’s linked to polygenetic inheritance?

Answer 27

Multifactorial inheritance

Question 28

What is multifactorial inheritance?

Answer 28

Gene-Environment Interaction = the appearance of the phenotype is contributed by the gene as well as the environment.

Question 29

What are examples of multifactorial inheritance?

Answer 29

1) Alcoholism
2) Sex orientation
3) Lung cancer